Persistent viral infections have been shown to reside in the host and cause various diseases. On the other hand, Drosophila melanogaster has been widely used as a model organism to study the immune responses against bacteria, fungi, parasites and viruses. Here, I present D. melanogaster as a model to study persistent virus infections. This book covers the strength of using this model system, describes viruses that infect it and give details about the Drosophila innate antiviral immunity. It furthermore explains about persistent infections and clarify definitions used in this field. It finally summarize the work of a newly discovered persistent RNA virus in Drosophila melanogaster, the Nora virus, and its biology and interaction with its host.